The present invention relates to improvements in fasteners. More particularly, the invention is directed to an improved screw-type fastener having a threaded shank and a head integral therewith, and adapted to be driven into a structure by axial rotation about its longitudinal central axis in a driving direction such that the head is countersunk.
Hithereto known screw-type fasteners suffer from a major drawback in that they undergo loosening after a certain period of time. Indeed, environmental conditions such temperature and/or humidity variations, vibrations, etc. cause such fasteners to axially rotate in a direction opposite the driving direction, resulting in loosening. This is especially true in the case of screws used for securing gyproc panels to a wooden structure, as well as screws used in watches, pressure gauges and compressors, for example, which are subject to vibrations.
Although the art is abundant in screws of various kinds, some even of intricate designs, none of the screw-type fasteners proposed so far has solved the above problem.